I used the one Audiovox makes, CCS100. I hear they may not be producing it any longer. For the speed sensor input, I tapped into the stock wire that drives the speedometer on the '97. You also have to tap into the vacuum line by the brake boost accumulator. Mine worked really well in the 4.0 and when I went TDI it still works great. I bought mine @ Pep Boys somewhere about the year 2000.

Pretty straight forward. Tap into the vacuum line ("T" fitting), find a place on the throttle body to pull the accelerator, tap into the foot brake switch, figure out which is the pulse wire (it runs the speedometer and comes from down by the emerg. brake drum) and use that signal to run the Audiovox "brain" .

Also make sure that your mount for the cable pull is straight. If it goes at an angle the in & out pulling of the cable to its housing will cause excessive ware on the cable and it will start fraying and eventually break & fail.

I know you ordered the Audiovox kit. I had really good luck with the Rostra Universal 250-1223 kit. They also have a dash flat control pad for cruise engage and such (nice touch, as the Defender steering column looks like a porcupine already). It is an electrical powered unit, not vacuum. Personally I always had issues with vacuum related units on both the Range Rovers and Discos. The lines developed leaks, which affected not only the cruise, but idle. It seems the hoses used for that part of the system where not as robust as the rest of the vacuum system. I have put the Rostra in both systems with a VSS and without. They have an optional sensor that will read magnets you attach to the drive shaft. The system worked like a champ on the really off the wall VW Westfalia Syncro 4WD camper van from the 80's, which creatively invented hills and such to slow it down.